Allow better image spacing behaviors

[hjmjohnson]

itkHoughTransformRadialVotingImageFilter.hxx

188
189 DoGFunctionPointer DoGFunction = DoGFunctionType::New();
190 //HACK: We probably want this to be true, but it would require updated reference data sets
191 DoGFunction->SetUseImageSpacing(false);
192

Changing this from (false) to (true) will improve the behavior for non-isotropic 1mm images, but that will also require a new set of reference images to be created.